1. Field Of The Invention:
The present invention relates to depthfinders for detecting fish and bottom depth, and for displacing a two-dimensional output in the form of a color LCD display device which does not "wash out" in bright sunlight.
2. The Prior Art:
A depthfinder/fishfinder is shown in U.S. Pat. No. 4,597,069 to Milano et al, wherein a microprocessor is used to supply information to a digital display. A digital multiplexer interfaces with the microprocessor and with an alarm, a depth measurement and a keel offset. A sonar transducer and transceiver are used to supply information to the microprocessor. An alarm is provided which has a repetition rate proportional to the number and size of fish detected. The depth of fish detected is displayed as well. Flowcharts are illustrated in this reference showing the various routines and functions performed by the microprocessor.
In Oota et al, U.S. Pat. No. 4,578,672 a color liquid crystal display device is shown which is capable of displaying three primary colors on a transparent substrate. A light source is required behind a panel through which light is projected, the three primary colors being combined in this way to permit formation of additional colors visually.
A color display system for use with ultrasonic sonar is shown in Yamamoto et al, in U.S. Pat. No. 3,964,012. Targets such as the surface and bottom of the sea, and schools of fish detected can be displayed in different colors according to this reference. The colors red, green, and blue are specifically provided for. Light-emitting diodes (LED's ) are energized and are mounted upon a rotary disc of a flasher-type display device and are energized or turned on independently or in combination, depending upon the target intensity. A display element requires a neon bulb, an electric motor for turning the rotary disc, and a suitable slip-ring connection to a sonar transmitter/receiver.
A sonar signal processing device, combined with a color display using a color cathode ray tube, is shown in Blue et al in U.S. Pat. No. 3,845,462. Here, three primary colors are used in the cathode ray tube to generate additional colors for use with a sonar display.
U.S. Pat. No. 4,328,493, to Shanks et al, shows a liquid crystal color display having a cathode ray tube and two color selective polarizers. A cell is switched in synchronism with different images supplied to the cathode ray tube. Two colors are specifically shown as produced in the device, these colors being green and red.
A color CRT display system for fish detectors is shown in Japanese patent No. 57-114871(A) in the name of Keisuke Honda et al, wherein a color CRT device is shown which detects fish as well as a profile of the underwater surface. Echo signals are used to generate the display.
In U.S. Pat. No. 4,556,286 to Uchida et al, relates to a multilayer guest-host liquid crystal display without polarizers. Here, at least two guest-host liquid crystal cells are superimposed one upon another, to produce a display. A colored image is created. Unlike prior art devices, no polarizer is required. A substantially clear image is thereby created corresponding to the pattern of the electrodes against the colored background. A high contrast image is produced against a colored background by the application of a relatively low voltage between the electrodes.
U.S. Pat. No. 4,396,250 to Wada et al shows a multilayer guest-host liquid display without polarizers. This device has two guest-host liquid crystal cells superimposed upon each other.
A sonar apparatus having improved gain control is shown in U.S. Pat. No. 4,420,824 to Weber. Here, a microprocessor is used together with a digital display to indicate depth as a function of time required to receive echo signals. An LED or liquid crystal display is taught as being usable in this patent. The microprocessor uses appropriate software to provide output of digital signals in communicating with the display and other devices.